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More data suggest there is no need for defibrillation threshold testing in patients receiving a first-time implantable cardioverter defibrillator (ICD), but it is too soon to rule out such testing, according to a study and commentary.
Researchers found no significant differences in the composite rate of severe complications, sudden cardiac death, or resuscitation at 2 years between patients whose devices were and were not tested (1.72% versus 1.02%), according to Michele Brignole, MD, from Ospedali del Tigullio in Lavagna, Italy, and colleagues.
All-cause mortality at two years was also similar between the two groups, they reported online in the Journal of the American College of Cardiology.
The authors concluded that defibrillation threshold testing has limited clinical relevance and that their results support eliminating the practice.
"The prevailing rationale for the routine evaluation of defibrillation thresholds has been to ensure appropriate sensing of ventricular fibrillation, system integrity, and effective defibrillation," wrote N.A. Mark Estes III, MD, from Tufts University School of Medicine in Boston, in an accompanying commentary.
Unlike older ICD technology, the newer devices "have considerably lowered the incidence of elevated defibrillation thresholds," and many physicians have abandoned the practice of testing altogether, Estes said.
There are also medico-legal considerations concerning threshold testing since it reflects a "historical standard of care," he wrote.
But until prospective randomized trials are conducted, the evidence for or against threshold testing will not be definitive, Estes explained.
Results of the SIMPLE (Shockless Implant Evaluation) trial, which randomized 2,500 patients to defibrillation threshold testing or no testing, should be available in a year, giving the field more conclusive evidence, he concluded.
For the current study, Brignole and colleagues enrolled 2,120 consecutive patients from 41 centers in Italy (836 patients underwent testing, while 1,284 did not). Threshold testing was performed at the discretion of the each center's standard practice and the frequency of testing varied considerably, ranging from 0% to 100% per center.
The average age of patients was 66 and about 80% were men.
The primary combined endpoint of severe complications during implant, sudden death, or resuscitation occurred in 18 and 16 patients in the tested and untested groups, respectively, after two years of follow-up. The difference between the two groups was negligible.
They concluded that this large, real-world study shows comparable outcomes between tested and non-tested ICDs.
SOURCE: MedPage Today